[EnergyPlus_Support] Re: ASHRAE 90.1 G3.1.1

["Jean marais" <jeannieboef@xxxxxxxxx>]

Could you include the componants of the additional cooling system inline with your current system, I.e. even if your ahu is serving multiple floors, if you included a dx unit inline with it and vav dampers with reheat at the zones, then you have added a cooling system on each floor. Where does one HVAC system end an another begin really. This kind of thing is so irritating. it doesn't help anyone. I share your frustration.

--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "Jim Dirkes" <jim@...> wrote:
>
> Miroslav,
> 
> I think that making the cooling setpoint high (e.g., 30C) is not sneaky.
> The approach recognizes the actual situation and provides a realistic
> comparison between the two systems.
> 
> I am pretty sure that modelers other than I  have used this approach and I
> think I have seen a LEED CIR on the topic which indicates it's OK.  I do not
> know the intentions of ASHRAE's 90.1 authors.
> 
> p.s. Nothing I say above is definitive - it's opinion.  Defensible and
> realistic, but opinion nonetheless.  The authors of 90.1 did a very good
> job, but I have never seen or heard an explanation of this particular
> requirement.
> 
>  
> 
> The Building Performance Team
> James V. Dirkes II, P.E., BEMP , LEED AP
> 1631 Acacia Drive NW
> Grand Rapids, MI 49504
> 616 450 8653
> 
>  
> 
> From: EnergyPlus_Support@xxxxxxxxxxxxxxx
> [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of Marcus
> Sent: Sunday, May 06, 2012 12:29 PM
> To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> Subject: Re: [EnergyPlus_Support] ASHRAE 90.1 G3.1.1
> 
>  
> 
>   
> 
> Hi Miroslav,
> 
> Yes, now I see your dilemma! I have never experienced this, but have some
> thoughts;
> 
> One overriding concern is the number of unmet hours. If you have no cooling
> system in your proposed design, do you still meet G3.1.2.2 unmet hours? If
> you do, you can argue that your proposed design for whatever reason does in
> fact not require any cooling. And it follows that you can model the proposed
> system and simply turn the cooling setpoint up so high that the system never
> turns on. This of course is equivalent to not having any cooling system, and
> therefore maybe you... forgot to model it... 
> 
> This argument is one that I have seen on the bldg-sim list, but I have never
> needed, nor can I vouch for it, since it seems a little sneaky. 
> 
> If you do need cooling to meet unmet hours, another method might be to just
> throw in a PTAC unit in each zone. Packaged VAV has DX cooling, as does
> PTAC, so maybe you could argue that this meets the requirement for Table
> G3.1 10.d. I guess it depends on how you strictly read "cooling system shall
> be identical". 
> 
> So again, I don't have any experience with this exact problem, you might
> want to get official confirmation!
> 
> Cheers,
> 
> Marcus
> -- 
> Marcus Jones,  M.Sc., LEEDRAP BD+C
> Freelance energy consultant
> Vienna, Austria
> 
> On Sun, May 6, 2012 at 10:52 AM, Miroslav Bratanov
> <miroslav_bratanov@...> wrote:
> 
>   
> 
> Thanks for your reply and directions, Marcus!
> 
> But it is the proposed model that bothers me. And this is why:
> 
> The building that I am modeling has only heating and outdoor air systems.
> Some spaces have heating only and others have heating and outdoor air
> supply.
> The heating system is with radiators, so following Table G3.1.10b for the
> Proposed Building Performance "Where an HVAC system has been designed, the
> HVAC model shall be consistent with design documents..." I have modeled the
> heating system using Baseboard:Convective:Water and the outdoor air systems
> using AirLoopHVAC.
> 
> The building does not have a cooling system designed, but Table G3.1.1b says
> that "All conditioned spaces in the proposed design shall be simulated as
> being both heated and cooled, even if no heating or cooling system is to be
> installed...".
> Also Table 3.1.10d says for the Proposed Building Performance that "Where no
> cooling system exists or no cooling system has been specified, the cooling
> system shall be identical to the system modeled in the baseline building
> design".
> From this I understand that my proposed design model shall have the systems
> as they are given in the design documents plus Packaged VAV with Reheat for
> the cooling. In other words the proposed model shall include the radiator
> heating system, outdoor air systems and also packaged VAV with reheat.
> Correct me if I am wrong, please!
> 
> Currently in my proposed model I have the following systems for each floor:
> Baseboard:Convective:Water for all zones that have radiators only
> Baseboard:Convective:Water and AirLoopHVAC for all zones that have radiators
> and outdoor air supply systems
> Also I have one AirLoopHVAC that connects zones located on two different
> floors.
> Thus, I fulfill the requirements of Table G3.1.10b for the Proposed Building
> Performance "Where an HVAC system has been designed, the HVAC model shall be
> consistent with design documents..."
> 
> Now, the problem is how to add the Packaged VAV with Reheat to the proposed
> model in order to fulfill the requirements of Table 3.1.10d for the Proposed
> Building Performance "Where no cooling system exists or no cooling system
> has been specified, the cooling system shall be identical to the system
> modeled in the baseline building design"?
> 
> If I am allowed to use only one Packaged VAV with reheat for each floor, I
> can not think of a way to add it to all other AirLoopHVACs that are already
> used to model the outdoor air systems.
> 
> Thank you!
> Miroslav
> 
> 
> 
> On  5.05.2012 18:46, Marcus wrote: 
> 
>   
> 
> Hi Miroslav,
> 
> Yes, you can only have one packaged unit per floor. After you know your
> baseline system type, forget about your proposed HVAC system. The baseline
> system is a completely new system providing heating, cooling, and
> ventilation, and has no elements of your proposed system. 
> 
> Fortunately, you can easily model system 5 with the
> HVACTemplate:System:PackagedVAV  and associated objects. So take your
> proposed.idf file, and delete all the HVAC components so you are just left
> with geometry and loads, then apply the HVACTemplate:System,
> HVACTemplate:Plant:Boiler, and finally the HVACTemplate:Zone:VAV objects to
> each zone. See the appropriate example file in the /examples directory. 
> 
> Let me know how it goes, and best regards from Vienna! 
> 
> Marcus
> -- 
> Marcus Jones,  M.Sc., LEEDRAP BD+C
> Freelance energy consultant
> Vienna, Austria
> 
> 
> 
> On Sat, May 5, 2012 at 3:47 PM, Miroslav Bratanov
> <miroslav_bratanov@...> wrote:
> 
>   
> 
> Hello Everyone,
> 
> I am modeling a 3 storeyed building for LEED. There is no cooling system 
> in the building and according to Table G3.1 of ASHRAE 90.1-2007 for the 
> proposed design model I have to use the same cooling system as in the 
> baseline design.
> The system for my baseline design is Packaged VAV with Reheat and also 
> according G3.1.1 "each floor shall be modeled with its own HVAC system".
> 
> Does "each floor shall be modeled with its own HVAC system" mean that 
> the baseline model can have only one HVAC system for each floor?
> 
> In my proposed design model, there are more than three outdoor air 
> systems on each floor. Each of these systems uses AirLoopHVAC. I know 
> that I can add more than one branch on an AirLoopHVAC but still I would 
> have to add a separate Packaged VAV with Reheat for each existing 
> AirLoopHVAC on the same floor which means more than one Packaged VAV 
> with Reheat per floor.
> 
> Another problem is that in my proposed design model there is an 
> AirLoopHVAC that supplies fresh air to spaces on two different floors.
> If I add the Packaged VAV with Reheat to the existing AirLoopHVAC then 
> it won't comply with G3.1.1. How to model the cooling system then?
> 
> Has anyone had such or similar case and what would be the solution?
> Any help is appreciated!
> 
> Miroslav
>




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